1. Field of the Inventions
The present inventions relate to a small planing boats which have a multi-cylinder engines including operation control devices which change deactivated cylinders in a phased manner, for example, corresponding to an engine speed when the engine speed reaches or exceeds a predetermined speed.
2. Description of the Related Art
Small planing boats are frequently driven with their throttle valve at large openings and/or fully opened. During such operation, the engine speed can exceed the maximum recommended speed (the “over-revolution state”) when, for example, air is drawn into the jet pump. Thus, in order to prevent discomfort that can from such over-revolution of the engine, some conventional small planing watercraft designs include devices for deactivating each cylinder of the engine in a phased manner when the engine speed exceeds a predetermined speed, to thereby prevent the engine from reaching an over-revolution state. For example, Japanese Patent Document JP-A-2002-371875 discloses such a design.
In this watercraft design, the cylinders are deactivated one after another during an over-revolution state. More particularly, the number of deactivated cylinders is gradually increased, thereby reducing rotational fluctuations while lowering the engine speed. This helps to further improve rider comfort, for example, when the over-revolution state is frequently repeated.